The subject matter disclosed herein relates to providing power and, in particular, to providing redundant power to a device.
Several types of devices require redundant power supplies of power to ensure proper operation. For example, consider the case of a linear variable differential transformer (LVDT) being used to measure linear displacement of an object. The LVDT typically includes three coils placed end-to-end around a core. The center coil is the primary winding and the other two coils act as secondary windings. The core is typically a cylindrical ferromagnetic core and is attached to the object whose position is to be measured.
In operation, an alternating current is driven through the primary winding, causing a voltage to be induced in each secondary windings proportional to its mutual inductance with the primary. As the core moves, these mutual inductances change, causing the voltages induced in the secondary windings to change. Based on a difference in the voltages induced in the windings, the location of the rod, and therefore the object, can be determined.
In the event that power is not supplied to the LVDT, the LVDT will give a reading that indicates that the object is at one of its possible end locations. Such an indication may cause, for example, other elements in the system where the object is located to shut down as a protection measure. For small operations, such a shut-down may not be overly problematic. On the other hand, consider the case where the LVDT is measuring the position of an object in a turbine. If power is lost to the LVDT it may cause shut down of the turbine. Such a shut down could mean that a power generation plant cannot meet its output requirements at a given time.
While an LVDT has been described, it shall be understood that any type of sensor may encounter the problems described above. In addition, devices other than sensors are also susceptible to providing invalid or misleading information when the power to them is disrupted.